The 2012 Great Lakes Water Quality Agreement states that “the Waters of the Great Lakes should allow for human consumption of fish and wildlife unrestricted by concerns due to harmful pollutants.”
Assessment highlights
The Fish Consumption indicator is based on the analysis of contaminants in the fillets of five fish species (Chinook Salmon, Coho Salmon, Lake Trout, Walleye and Lake Whitefish) commonly eaten in the Great Lakes. The status of contaminants in the fillets is assessed as Fair and the 10-year trend is Improving. Many contaminants in fish fillets have declined dramatically in the Great Lakes compared to levels measured 40-50 years ago. After an initial period of rapid decline following bans and phaseouts of certain chemicals, contaminant levels in Great Lakes fish fillets have shown a slower rate of decline over the past 25-30 years. This moderated decline can be attributed to factors such as chemical persistence, reintroduction from historically contaminated sediments, and invasive species-driven changes to the Great Lakes food web. The rate of decline also depends on fish size, age, diet, and lipid content. Additionally, water temperature can influence how contaminants are taken up, stored, and metabolized by fish.
In the Great Lakes, fish consumption advisories primarily result from elevated PCBs and mercury concentrations, with PCBs driving the majority of advisories in both the U.S. and Canada. PCBs in fish fillets have decreased by over 90% for some fish species in some lakes since the 1970s. Mercury levels in fish fillets have generally declined by half over the last 40-50 years. Based on PCB and mercury concentrations, conditions are considered Good in lakes Superior, Huron and Erie and Fair in lakes Michigan and Ontario. The overall status assessment for this indicator is Fair, with signs of improvement in some monitored fish species, resulting in less restrictive fish consumption advice for some areas, in particular in Lake Erie.
Over the past 10 years, PCB concentrations in fish fillets have declined or remained unchanged in all of the lakes. During this same period, mercury concentrations in fish fillets have remained stable or decreased slightly. On this basis, the trend is assessed as Improving.
Other contaminants, such as per- and polyfluoroalkyl substances (PFAS) have recently prompted issuance of fish consumption advisories for some areas of the Great Lakes. PFAS are responsible for approximately 10% of the advisories issued in Canadian waters of the Great Lakes.
Mercury concentrations in Lake Trout fillets have declined substantially since the 1970s and 1980s
Sub-indicator supporting the Fish Consumption assessment
Sub-Indicator | Lake Superior | Lake Michigan | Lake Huron | Lake Erie | Lake Ontario |
Contaminants in Fish Fillets | Good & Improving | Fair & Improving | Good & Unchanging to Improving | Good & Improving | Fair & Unchanging to Improving |
Status
